Developing methods for efficient energy storage systems, which is also environmentally benign, has been an emerging field in the research programmes due to intermittent nature of energy from the renewable energy sources. Among the various energy storage devices, energy storage systems such as batteries and supercapacitors, which store energy electrochemically are highly preferred due to their efficient storage capacity and also since the processes are environmentally friendly.
Electrochemical supercapacitors, as potential candidates for energy storage, are very promising over batteries such as lithium ion batteries in terms of their high power density, fast charge-discharge rate, high columbic efficiency and long cycle life.
However, liquid electrolytes in the conventional electrochemical energy storage devices raise safety issues and thus require high-standard safety encapsulation materials and technology. Replacement of liquid electrolyte in the energy storage devices using a solid counterpart is very promising for the thin, light, cheap and flexible future devices.
Polymer electrolytes have been extensively studied as electrolytes in supercapacitors and lithium batteries. Among the various polymer electrolytes, gel/plasticised electrolytes6 show ambient conductivity and desirable mechanical properties and are promising as electrolyte materials to replace conventional liquid electrolyte in supercapacitor. Many of the earlier studies utilized gel/plasticised electrolyte to replace conventional liquid electrolyte in supercapacitor. However, the use of gel as a film between the electrodes resulted in low electrode-electrolyte interfacial area which in turn resulted in poor charge storage properties.
Apart from the low charge storage property, the above strategy increases the total device resistance due to high contact resistance9 arising from the low integrity of electrode electrolyte material. Very low internal resistance (or ESR) for storage device is highly desirable as the power rate of the device is determined by the relation Pmax=v2/4R.
In order to replace liquid electrolyte from the supercapacitor (or lithium battery and fuel cell) with solid counterpart, there is a need for an electrode-electrolyte interface that can mimic the liquid-solid interface and yet provide enhanced electrode-electrolyte interface which can help the device to attain a very low ESR, which leads to high specific capacitance, areal capacitance and show excellent cycle stability.
All solid state supercapacitors are known in the art and are disclosed in patents/Patent applications such as US2012014038, US2013083452, WO201401194, CN102509637, and CN103337376 among others. However, the all-state solid supercapacitors known in the art have the following limitations/disadvantages:    i. They show low specific capacitance and areal capacitance.    ii. Current collector is used. During electrode making additive like conducting carbon and binder are used.    iii. Complicated fabrication strategy is used.
The present inventors have therefore focussed in providing all solid state supercapacitor with enhanced electrode-electrolyte interface which gives very high specific capacitance, areal capacitance and shows very low internal resistance (ESR).